The present invention relates generally to a substrate processing apparatus and a method of manufacturing a semiconductor device and, more particularly, to a substrate processing apparatus capable of preventing a reaction product from being deposited on a cell portion of an outer tube in a vertical type CVD apparatus and a method for manufacturing a semiconductor device using the substrate processing apparatus.
FIG. 7 illustrates a longitudinally front sectional view of a vertical type CVD apparatus conventionally used as a substrate processing apparatus. In this substrate processing apparatus, there are provided within a heater 1 an outer tube 2 and an inner tube 3 which is disposed in the outer tube 2 and accommodates therein a boat 4 carrying a plurality of semiconductor substrates (semiconductor wafers), e.g., 5a, 5b for depositing or forming a film on each surface of the semiconductor substrates.
FIG. 8 is a schematic sectional view showing a bottom portion of a reaction chamber (as designated by xe2x80x9cAxe2x80x9d in FIG. 7) of the substrate processing apparatus. A gas supply to the substrates is performed by introducing a gas from a gas-introducing port 6 of an adapter 7 into the inner tube 3, so as to upwardly flow along the substrates and consecutively flow into a space between an outer-wall of the inner tube 3 and an inner-wall of the outer tube 2 and then discharged outwardly via an exhaust pipe 8.
FIG. 9 is a schematic sectional view showing an upper portion of the substrate processing apparatus in order to illustrate an inherent problem of this substrate processing apparatus. Although such a gas circulation through the apparatus caused by the gas supply is performed as mentioned above, a reaction product 9 will be deposited on a ceiling portion of the outer tube 2 during the above-noted film deposition on the substrates, as shown in FIG. 9, and disadvantageously adhered to the processed or processing substrates as particles when the reaction product 9 is peeled from the ceiling portion.
In order to solve this problem, there is proposed a vertical type CVD apparatus comprising an outer tube and inner tube in Japanese Patent Laid-Open Publication No. HEI 6-275533. In particular, the inner tube is configured to have a closed top end, an exhaust opening provided on a side wall thereof in vicinity of the closed top end and an introducing port for a reaction gas located on a lower end portion thereof. The exhaust opening is in communication with an interior of the outer tube, i.e., a space defined between the outer tube and inner tube.
According to this prior art, the closed top end of the inner tube is flat or in the form of an inverted cup. Thus, a gas flow which flows upwardly in the inner tube can not be smoothly deflected into the outer tube but rather tends to be held up or stayed at the closed top end within the outer tube, as a result of which it is difficult to uniformly process semiconductor substrates with a high quality or there is a fear not to manufacture semiconductor devices on the substrate.
Thus, the present invention is accomplished to solve the problems as mentioned above.
In order to solve the problems as noted above, according to a first aspect of the present invention, there is provided a substrate processing apparatus, wherein a flowing direction of a gas flow which has flown upwardly and ascended in an inner tube is changed at an upper portion of the inner tube so as to be flown between the inner tube and an outer tube and exhausted outwardly, comprising: a gas flow-deflecting member consisting a cap portion for covering an open top end in the upper portion of the inner tube and a support portion for supporting said cap portion, said support portion being mounted on a circumferential edge of the open top end of the inner tube, and said cap portion being in the form of an inverted cone having a central portion protruded into an upstream of the gas flow; and gas passages provided between the open top end of the inner tube and said cap portion.
In particular, the inverted cone, which shapes the cap portion, has a tip end positioned a downstream side of the gas flow than a bottom end of said support portion.
According to a second aspect of the present invention, there is provided a substrate processing apparatus, wherein a flowing direction of a gas flow which has flown upwardly and ascended in an inner tube is changed at an upper portion of the inner tube so as to be flown between the inner tube and an outer tube and exhausted outwardly, comprising: a gas flow-deflecting member for covering the upper portion of the inner tube; gas passages provided between the upper portion of the inner tube and the gas flow-deflecting member; said gas flow-deflecting member having a central portion protruded into an upstream of the gas flow; and a heater for heating substrates carried in the substrate processing apparatus, wherein a top end of said heater is extended up to a higher position than a top end of the outer tube.
According to a third aspect of the present invention, there is provided a method for manufacturing a semiconductor device comprising the steps of: carrying at least one substrate in an inner tube, heating the substrate, flowing a gas upwardly in said inner tube, changing direction of the gas flow by a gas flow-deflecting member, consisting a cap portion for covering an open end in the upper portion of the inner tube and a support portion for supporting said cap portion, said support portion being mounted on a circumferential edge of the open top end of the inner tube, and cap portion being in the form of an inverted cone, flowing the gas downwardly through the inner tube and an outer tube so as to exhaust outward of the outer tube.
With an arrangement as described above, the flowing direction of a gas which has flown upwardly within the inner tube and ascended to the upper portion of the inner tube is changed in a transverse direction by the gas flow-deflecting member which is disposed on the open top end of the inner tube to flow the gas through gaps defined between the top end of the inner tube and the gas flow-deflecting member and then into a space between the outer tube and the inner tube downwardly. Therefore, a ceiling portion of an outer tube is prevented from being directly exposed to a gas uprising in the inner tube, thereby preventing a reaction product from be deposited on the ceiling portion. Also, even if the reaction product is allowed to be deposited on the ceiling portion and then peeled off or dropped therefrom, the gas flow-deflecting member can receive their droppings as particles on its upper surface to prevent them from being adhered to or deposited on a wafer(s). Since the gas flow-deflecting member is in the form of an inverted cone having a protruded center directed downwardly to an upstream of the gas flow, the reaction gas is disenabled to hold up or stay thereat. Further, since the protruded center of the gas flow-deflecting member is positioned or configured to be approximate to a high-temperature side location within a furnace, the gas flow-deflecting member is able to avoid deposition of the reaction product on itself.
Thus, according to the present invention, it is possible to allow the substrate to be uniformly processed with a high quality and uniformly manufacture semiconductor devices on the substrate with a high quality. Also, the gas flow-deflecting member may directly be mounted on the circumferential edge of the open top end of the inner tube, be disposed on an upper end portion of a boat accommodated in the inner tube, or be suspended from the ceiling portion of the outer tube. Furthermore, in order to more efficiently introduce a gas flow into a space defined between the inner tube and the outer tube, the gas flow-deflecting member may include an eave along a periphery thereof.
In an embodiment of the present invention as described below, the gas flow-deflecting member as an inner-tube cap is made of the same material as that for the inner tube which is made of quartz. Therefore, the gas flow-deflecting member has the same thermal expansion as that of the inner tube, thereby effectively preventing a misalignment between the inner tube and the gas flow-deflecting member due to a difference of thermal expansion. Also, in the embodiment as described below, a heaters are extended up to and in a surrounding relation to an upper portion of a reaction tube to such an extent as sufficiently heating the gas flow-deflecting member, thereby effectively preventing a reaction product from being deposited on the gas flow-deflecting member.